Magnetic field sensing device and method for fabricating thereof

ABSTRACT

Disclosed is a magnetic field sensor of high sensitivity, and which is power-saving and can be manufactured with low cost in a very small size. The magnetic field sensor includes a soft magnetic core formed to construct a closed-magnetic circuit on a semiconductor substrate, a magnetic field sensing coil formed by a metal film in a shape that winds the soft magnetic core, and a drive line for exciting the soft magnetic core by directly applying an electric current thereto. The drive line is formed in a rectangular angle to the magnetic field sensing coil, and connected to the both ends of the soft magnetic core in a length direction.

This is a divisional of application Ser. No. 10/773,456 filed Feb. 9,2004 now U.S. Pat. No. 7,071,688. The entire disclosure of the priorapplication, application Ser. No. 10/773,456 is hereby incorporated byreference.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Korean Application No.2003-08343, filed Feb. 10, 2003, in the Korean Intellectual PropertyOffice, the disclosure of which is incorporated herein by reference.

BACKGROUND

1. Field of the Invention

The present invention relates to a sensor for a magnetic field, and morespecifically, to a magnetic field sensor integrated in a semiconductorsubstrate and a method for fabricating the same.

2. Description of the Related Art

Existence of magnetic energy has been proven through various physicalphenomena, and a magnetic field sensor enables a human to indirectlyperceive magnetic energy, as it is unperceivable to human sense organssuch as eyes and ears. As for the magnetic field sensor, a magneticsensor employing a soft magnetic material and a coil has been used for along time. The magnetic sensor is made by winding a coil around arelatively large bar-shaped core or an annular core formed of a softmagnetic ribbon. Also, an electronic circuit is employed to obtain amagnetic field in proportion to the measured magnetic field.

The conventional magnetic field sensor, however, has the followingproblems. That is, due to the structure of the conventional magneticfield sensor in which the coil is wound around a large bar-shaped coreor an annular core made of soft magnetic ribbon, production costs arehigh, and the volume of the overall system is large.

Also, flux leakage is inevitable in the flux change due to theexcitation coil and the detected magnetic field. Accordingly, highsensitivity cannot be guaranteed.

SUMMARY

The present invention has been made to overcome the above-mentionedproblems of the prior art. Accordingly, it is an object of the presentinvention to provide a high sensitivity magnetic field sensor integratedin a semiconductor substrate capable of not only reducing manufacturingcost and overall volume of a system, but also detecting a magnetic fieldwith more accuracy.

It is another object of the present invention to provide a method formanufacturing such a highly sensitive magnetic field sensor integratedin a semiconductor substrate capable of not only reducing manufacturingcost and overall volume of a system, but also detecting a magnetic fieldwith more accuracy.

In order to achieve the above-described objects of the presentinvention, there is provided a magnetic field sensor integrated in asemiconductor substrate, comprising a soft magnetic core formed in asemiconductor substrate to construct a closed-magnetic circuit, amagnetic field sensing coil formed by a metal film in a structure ofwinding magnetic core, and a drive line for exciting the soft magneticcore by directly applying an electric current thereto.

Here, the drive line is formed in a rectangular angle to the magneticfield sensing coil and connected to both ends of the soft magnetic corein a length direction. The length direction of the soft magnetic core isin a magnetic field sensing axis.

In addition, the magnetic field sensing coil is wound in a solenoidpattern.

According to another aspect of the present invention, in order toachieve the above objects, there is provided a method for fabricating amagnetic field sensor integrated in a semiconductor substrate,comprising the steps of forming a pattern on a semiconductor substrate,corresponding to a lower part of the magnetic field sensing coil, andforming the lower part by first-putting metal into the pattern, forminga first insulation film on the semiconductor substrate where the metalis first-put, accumulating a soft magnetic material film on the firstinsulation film, and forming a soft magnetic core by patterning andetching, forming a second insulation film on the semiconductor substratewhere the soft magnetic core is formed, forming on the second insulationfilm a penetrating hole for fluidly communicating with the first-putmetal forming the lower part, and also forming a penetrating hole forfluidly communicating with the soft magnetic core, forming a patterncorresponding to an upper part and a soft magnetic core terminal of themagnetic field sensing coil on the second insulation film, and formingthe upper part and the soft magnetic core terminal by second-puttingmetal into the pattern, forming a protection film on the semiconductorsubstrate where the metal is second-put, and opening the protection filmso that the magnetic field sensing coil and the soft magnetic coreterminal are connected with electric power.

Here, the method for formimg of the lower part of the magnetic fieldsensing coil comprises the steps of forming an oxide film on thesemiconductor substrate, forming a conductive film on the oxide film,applying a photoresist on the conductive film, forming a patterncorresponding to a lower part of the magnetic field sensing coil byexposure and development, first-putting metal into an upper part of thesemiconductor substrate such that the metal is filled in the patternedarea, and removing the photoresist remaining after forming the pattern,and the conductive film which is the lower part of the remainingphotoresist.

Additionally, the method for forming the soft magnetic core comprisesthe steps of forming a metal film on the first insulation film, applyinga photoresist on the metal film, forming a pattern on the photoresist,corresponding to the soft magnetic core, by exposure and development,and removing the metal film on the area except for the patterned area,and removing the photoresist remaining after forming the pattern.

Further, the method for forming an upper part of the soft magnetic corecomprises the steps of forming a conductive film on the secondinsulation film where the penetrating hole is formed, applying aphotoresist on the conductive film, forming a pattern on thephotoresist, corresponding to an upper part of the magnetic fieldsensing coil, by exposure and development, second-putting metal to fillin the patterned area, and removing the photoresist remaining afterforming the pattern and the conductive under the remaining photoresist.

Here, the soft magnetic core terminal is preferably formed on both endsof the soft magnetic core in a length direction.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of the presentinvention will become better understood with regard to the followingdescription, appended claims, and accompanying drawings where:

FIG. 1 is a plan view of a magnetic field sensor which is integrated ina semiconductor substrate according to a preferred embodiment of thepresent invention;

FIG. 2 is a sectional view of the structure of the magnetic field sensorintegrated in a semiconductor substrate according to the presentinvention;

FIG. 3 is a view for illustrating a magnetic field generated on a softmagnetic core by an exciting current in the magnetic field sensor ofFIG. 2; and

FIGS. 4A through 4K are sectional views cut along I–I′ line and II–II′line of FIG. 1 for respectively showing processes of fabricating themagnetic field sensor of FIG. 1 in a semiconductor substrate.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, preferred embodiments of a magnetic field sensor integratedin a semiconductor substrate and a method for fabricating the sameaccording to the present invention will be described in detail withreference to the accompanying drawings.

FIG. 1 is a plan view of a magnetic field sensor which is integrated ina semiconductor substrate according to a preferred embodiment of thepresent invention. Referring to FIG. 1, the magnetic field sensorcomprises a soft magnetic core 40 shaped in a rectangular bar, amagnetic field sensing coil 20 winding the soft magnetic core 40 in asolenoid pattern, and a drive line 50 connected to both ends of the softmagnetic core 40. The magnetic field sensor according to the presentinvention does not use a separate coil to magnetize the soft magneticcore 40, but senses an external magnetic field using an excitingmagnetic field which is generated as an electric current is applieddirectly to the soft magnetic core 40 through the drive line 50. Thatis, unlike the conventional magnetic field sensor, the magnetic fieldsensor according to the present invention does not use the exciting coilfor generating the exciting magnetic field. A reference numeral 20 a ofFIG. 1 is a coil pad for connecting the magnetic filed sensing coil 20to an external electric circuit (not shown), and a reference numeral 50a is a power pad for connecting an external electric power (not shown)to the drive line 50 applying the electric current to the soft magneticcore 40.

In FIG. 2, there is illustrated a sectional structure of the magneticfield sensor integrated in the semiconductor substrate. Referring toFIG. 2, an insulation film 11 is formed on the semiconductor substrate10, and a lower part 22 of the magnetic field sensing coil 20 is formedon the insulation film 11. On an upper part of the lower part 22, thesoft magnetic core 40 is formed. On the upper part of the soft magneticcore 40, an upper part 26 of the magnetic field sensing coil 20 isformed. Albeit not shown, the lower part 22 and the upper part 26 arefluidly communicated, to permit a coil to pass therethrough to wind thesoft magnetic core 40 in a solenoid pattern. The soft magnetic core 40is covered by an insulation material 30, and thus is insulated from themagnetic field sensing coil 20. Additionally, to the both ends of thesoft magnetic core 40, drive lines 50 are connected to apply an excitingcurrent to the soft magnetic core 40. The drive lines 50 are arranged ina rectangular angle as to the respective coils constructing the magneticfield sensing coil 20.

Hereinafter, the operation of the magnetic field sensor integrated inthe semiconductor substrate will be described.

When an electric current is applied through the drive line 50, anexciting magnetic field 42 is generated inside the soft magnetic core40, as shown in FIG. 3. By the exciting magnetic field 42, the softmagnetic core 40 is magnetized. More specifically, due to a strongdiamagnetism, magnetization occurs rarely in a thickness direction ofthe soft magnetic core 40, but usually in the exciting magnetic field 42direction on the surface and the bottom side of the soft magnetic core40. Such magnetization direction is in parallel relation to respectivecoils of the magnetic field sensing coil 20 which is wound on the softmagnetic core 40 in a solenoid pattern. The magnetization by theexciting magnetic field 42 on the soft magnetic core 40 varies dependingon the extent of the exciting current flowing to the drive line 50 andthe waveform thereof. Yet, in the embodiment of the present invention,since the magnetization direction of the soft magnetic core 40 isparallel to the coil winding direction of the magnetic field sensingcoil 20, variation of the induction waveform according to change of theexciting current does not occur on the magnetic field sensing coil 20.Accordingly, when an external magnetic field to measure is zero, thereoccurs no induction waveform on the magnetic field sensing coil 20.

In such state, when an external magnetic field operates in a lengthdirection of the soft magnetic core 40, a voltage is induced on themagnetic field sensing coil 20. Accordingly, the external magnetic fieldcan be sensed by connecting the voltage to an external electric circuit.

A magnetic field sensor of the above structure does not need a separateexciting coil for magnetizing a soft magnetic core. Therefore, it isadvantageous that intervals between coils can be cut down to the half,compared with a general conventional magnetic field sensor which iswound by a magnetic field sensing coil and an exciting coil by turns.Further, since the soft magnetic core 40 functions as the exciting coil,resistance can be changed freely by controlling a shape and a thicknessof the soft magnetic core 40. Accordingly, power consumption can besaved by reducing the resistance of the soft magnetic core. Therefore,according to the present invention, the resistance of the soft magneticcore 40 which is the exciting coil can be minimized. In addition, theintervals of the magnetic field sensing coil can also be reduced to adegree of line-width fabrication of the current integrated circuit,thereby providing a magnetic field sensor of which the output of powerand the sensitivity are remarkably increased.

FIGS. 4A through 4K are sectional views cut along I–I′ line and II–II′line of FIG. 1 for respectively showing processes of fabricating themagnetic field sensor on a semiconductor substrate. In FIGS. 4A through4K, the drawings on the left are sections of the magnetic field sensorbeing cut along the I–I′ line, and the drawings on the right are thesections being cut along the I′–II′ line.

Hereinafter, the fabrication process of the magnetic field sensorintegrated in a semiconductor substrate will be described in greaterdetail with reference to the accompanying drawings.

First, a pattern according to the lower part 22 of the magnetic fieldsensing coil 20 is formed, on a semiconductor substrate 10, and thelower part 22 is formed by primarily inserting metal into the pattern. Apreferred embodiment of the process of fabricating the lower part 22will now be described in detail.

An oxide film 11 for insulating is formed on the semiconductor substrate10, and a conductive film 21 is formed on the oxide film 11. Theconductive film 21 may have a function of applying an electric currentlater in case of plating by an electrolytic plating, as shown in FIG.4A. Here, the material for forming the conductive film can be Cr or Auwhich are used in fabricating a general semiconductor.

On the conductive film 21, a photoresist 23 is applied to form the lowerpart 22 of the magnetic field sensing coil 20, and the pattern of thelower part 22 is formed by exposure and development, as shown in FIG.4B.

Later, the lower part 22 is formed as metal is inserted into thedepression 24 of the pattern of the lower part 22, as shown in FIG. 4C.At this time, for filling the metal in the pattern of the lower part 22,an electrolytic plating is preferably used. Then, the metal isintegrated in the conductive film 21 which is the exposed depression 24of the pattern, and thereby forming the lower part 22 of the magneticfield sensing coil 20. When the lower part 22 is completed, thephotoresist 23 used to form the pattern is removed, and the conductivefilm 21 disposed under the photoresist 23 is removed such that therespective coils are insulated from each other, as shown in FIG. 4D.

Then, a first insulation film 30 is formed on the semiconductorsubstrate 10 on which the lower part 22 is formed, as shown in FIG. 4E.

Then, a soft magnetic material film is integrated on the firstinsulation film 30, and the soft magnetic core 40 is formed bypattern-forming and etching. The process of forming the soft magneticcore 40 is described below in greater detail.

First, a soft magnetic material film is formed on the first insulationfilm 30, and the photoresist 23 is applied on the soft magnetic materialfilm. Then, a pattern according to the soft magnetic core 40 is formedon the photoresist 23 by exposure and development. Next, the softmagnetic material film on the area where is patterned by etching isremoved to form the soft magnetic core 40. After the soft magnetic core40 is formed, remaining photoresist which was for the pattern of thesoft magnetic core 40 is removed, as shown in FIG. 4F.

A second insulation film 32 is formed on the semiconductor substrate 10where the soft magnetic core 40 is formed, and then a penetrating hole29 which is fluidly communicated with the first-put metal forming thelower part 22 is formed. Here, near the both ends of the soft magneticcore 40 in a length direction, penetrating holes 42 are also formed forfluidly communicating with the soft magnetic core 40, as shown in FIG.4G.

A pattern for the upper part 26 of the magnetic field sensing coil 20 isformed on the second insulation film 32, and then metal is secondarilyput into the pattern to form the upper part 26. The process offabricating the upper part 26 will be described in great detail throughthe following preferred embodiment.

First, a conductive film 25 is formed on the second insulation 32 wherethe penetrating holes 29, 42 are formed, and a photoresist 34 is appliedon the conductive film 25. Next, patterns corresponding to the upperpart 26 and a soft magnetic core terminal 50 are formed on thephotoresist 34 by exposure and development, as shown in FIG. 4H.

Then, in a depression 27 of the pattern of the upper part 26 and thedepression 42 of the soft magnetic core terminal 50, metal issecond-put, and thereby the upper part 26 and the soft magnetic coreterminal 50 are formed. At this time, it is preferable that anelectrolytic plating is used for filling the metal in the patterns ofthe upper part 26 and the soft magnetic core terminal 50. Accordingly,the metal is integrated in the conductive film 25 which is the exposeddepressions 27, 42 of the pattern, and thereby forming the upper part 26and the soft magnetic core terminal 50. When the upper part 26 and thesoft magnetic core terminal 50 are completely formed, the photoresist 34forming the patterns is removed. Then, the conductive film 25 under thephotoresist 34 is removed such that the respective coils of the magneticfield sensing coil 26 and the soft magnetic core terminal 50 areinsulated from each other.

Afterward, a protection film 60 is applied on the semiconductorsubstrate 10 where the upper part 26 is formed, and a penetrating hole61 for fluidly communicating with the soft magnetic core terminal 50 anda penetrating hole (not shown) for fluidly communicating with themagnetic field sensing coil 20 are formed on the protection film 60.Thereby, the fabrication of the magnetic field sensor is completed.

As described above, the magnetic field sensor according to the presentinvention employs the soft magnetic core for the exciting coil.Therefore, the magnetic field sensing coil 20 can be formed compactly,having intervals thereof for forming line-width of the currentintegrated circuit, thereby improving the magnetic field sensitivity.Further, since the resistance of the soft magnetic core 40 can bereduced by controlling the shape and the thickness of the soft magneticcore, there can be provided a magnetic field sensor which ispower-saving. Additionally, since an aspect ratio of the magnetic fieldsensing coil 20 does not have to be large to increase the sensitivityand save power consumption, the fabrication process becomes simple, alsoenabling mass-production by a semiconductor fabrication process, whichcauses a lower manufacturing cost.

As described above, the magnetic field sensor integrated in asemiconductor substrate according to the present invention can measurethe magnetic field precisely with less power consumption. In addition,according to the present invention, a magnetic field sensor can beprovided in a very small size and with economical in manufacturing cost.

Additionally, according to the fabrication process of the magnetic fieldsensor integrated in a semiconductor substrate according to the presentinvention, a magnetic field sensor can measure the magnetic fieldprecisely, and can be provided in a very small size and economical inmanufacturing cost.

While the invention has been shown and described with reference tocertain preferred embodiments thereof, it will be understood by thoseskilled in the art that various changes in form and details may be madetherein without departing from the spirit and scope of the invention asdefined by the appended claims.

1. A method for fabricating a magnetic field sensor comprising the stepsof: forming a pattern on a semiconductor substrate, corresponding to alower part of the magnetic field sensing coil, and forming the lowerpart by first-putting metal into the pattern; forming a first insulationfilm on the semiconductor substrate where the metal is first-put;accumulating a soft magnetic material film on the first insulation film,and forming a soft magnetic core by patterning and etching; forming asecond insulation film on the semiconductor substrate where the softmagnetic core is formed; forming on the second insulation film apenetrating hole for fluidly communicating with the first-put metalforming the lower part, and also forming a penetrating hole for fluidlycommunicating with the soft magnetic core; forming a patterncorresponding to an upper part of the magnetic field sensing coil on thesecond insulation film, and forming the upper part by second-puttingmetal into the pattern; and forming a protection film on thesemiconductor substrate where the metal is second-put.
 2. The method forfabricating a magnetic field sensor of claim 1, wherein the method forformimg of the lower part of the magnetic field sensing coil comprisesthe steps of: forming an oxide film on the semiconductor substrate;forming a conductive film on the oxide film; applying a photoresist onthe conductive film; forming a pattern corresponding to a lower part ofthe magnetic field sensing coil by exposure and development;first-putting metal into an upper part of the semiconductor substratesuch that the metal is filled in the patterned area; and removing thephotoresist remaining after forming the pattern, and the conductive filmwhich is the lower part of the remaining photoresist.
 3. The method forfabricating a magnetic field sensor of claim 1, wherein the method forforming the soft magnetic core comprises the steps of: forming a softmagnetic material film on the first insulation film; applying aphotoresist on the soft magnetic material film; forming a pattern on thephotoresist, corresponding to the soft magnetic core, by exposure anddevelopment; removing the soft magnetic material film except for thepatterned area; and removing the photoresist remaining after forming thepattern.
 4. The method for fabricating a magnetic field sensor of claim1, wherein the method for forming an upper part of the soft magneticcore comprises the steps of: forming a conductive film on the secondinsulation film where the penetrating hole is formed; applying aphotoresist on the conductive film; forming a pattern on thephotoresist, corresponding to an upper part of the magnetic fieldsensing coil, by exposure and development; second-putting metal to fillin the patterned area; and removing the photoresist remaining afterforming the pattern and the conductive under the remaining photoresist.5. The method for fabricating a magnetic field sensor of claim 1,wherein the penetrating hole fluidly communicated with the soft magneticcore is formed on both ends of the soft magnetic core in a lengthdirection.
 6. The method for fabricating a magnetic field sensor ofclaim 5, wherein the length direction of the soft magnetic core isformed toward magnetic field sensing axis.
 7. The method for fabricatinga magnetic field sensor of claim 1, wherein the magnetic field sensingcoil is wound in a solenoid pattern.